tellme_why

Good day, May I ask your advice for an owner-occupied dwelling (about 120 sqm) built in the sixties and extended (one kitchen + bigger lounge) in 1995. What is the minimum building regulation requirements for smoke/fire alarm; shall a class F (battery operated) or class D (mains powered) system? I would like to avoid class D system since it requires new cables and the ceiling has just been plastered and painted.. so I would prefer a battery only system... many thanks